BTW, I have purchased a very interesting article from SoS about the making of Bon Iver's latest album, and I thought I might copy/paste here the part specifically related to the "Messina"
Messina elaborates on how he devised the Messina. “Inspired by what Francis did, Justin and I got together and we tried every single vocoder that was listed, but they all sounded
like a vocoder, which was not exactly what we wanted. Instead we wanted to be able to keep
the character of whatever input signal we used, whether a voice or a saxophone. So instead we developed this thing which basically is a glorified vocoder. The input signal goes into Ableton Live where it is treated by two Auto-Tune plug-ins. The first just tunes the vocal, in the way Justin has always done it, and the second plug-in creates just a single note, the tonic of the key of the phrase that is sung or played, and that then
is sent to an Eventide H8000, which is set to a MIDI harmony program.
“Justin can play the white keys of a MIDI keyboard at the same time, and the H8000 receives the Auto-Tune tonic input, sometimes a dry input, and the input of the MIDI keyboard, and the H8000 generates up to four notes based on what’s played. It involves a degree of randomisation, so you don’t know exactly what you’re going to get. We’d then use a combination of the dry signal, tuned signal, tonic signal and the harmony created by the H8000 to make the ‘Messina’ sound. A lot of the distortion on the album comes from this, because the H8000 program naturally creates a lot of artifacts. When you’re switching keys on the MIDI keyboard it automatically creates this kind of clicking noises as it’s changing whatever harmonies it’s creating. We removed some of those clicking noises, but as also left many in, because we liked them. But a lot of the distortion is Justin and the Messina, with the H8000 doing what it does to the signal. You can hear Justin on his own with the Messina in ‘715’. That song is mostly just one take, though we did do a few additional takes, hitting the 8000 differently each time, cranking up the output to hit it harder. The way the 8000 reacts to different input signals can be pretty cool.”